Page 298 - DCAP101_BASIC_COMPUTER_SKILLS

Unit 14: Web Server Applications

14.3 Instant Messaging (IM) Notes

Instant messaging (IM) is a form of real-time direct text-based communication between two
or more people using personal computers or other devices, along with shared clients. The
user’s text is conveyed over a network, such as the Internet. More advanced instant messaging
software clients also allow enhanced modes of communication, such as live voice or video
calling.

14.4 Internet Telephony

A category of hardware and software that enables people to use the Internet as the transmission
medium for telephone calls. For users who have free or fixed-price Internet access, Internet
telephony software essentially provides free telephone calls anywhere in the world. To date,
however, Internet telephony does not offer the same quality of telephone service as direct
telephone connections.
There are many Internet telephony applications available. Some, like CoolTalk and
NetMeeting, come bundled with popular Web browsers. Others are stand-alone products.
Internet telephony products are sometimes called IP telephony, Voice over the Internet (VOI)
or Voice over IP (VOIP) products.

14.5 Videoconference

A videoconference or video conference (also known as a videoteleconference) is a set of
interactive telecommunication technologies which allow two or more locations to interact
via two-way video and audio transmissions simultaneously. It has also been called ‘visual
collaboration’ and is a type of groupware.
Videoconferencing differs from videophone calls in that it is designed to serve a conference
rather than individuals. It is an intermediate form of videotelephony, first deployed
commercially by AT&T during the early 1970s using their Picturephone technology.
The core technology used in a videoconferencing system is digital compression of audio and
video streams in real time. The hardware or software that performs compression is called
a codec (coder/decoder). Compression rates of up to 1:500 can be achieved. The resulting
digital stream of 1s and 0s is subdivided into labeled packets, which are then transmitted
through a digital network of some kind (usually ISDN or IP). The use of audio modems in
the transmission line allow for the use of POTS, or the Plain Old Telephone System, in some
low-speed applications, such as videotelephony, because they convert the digital pulses to/
from analog waves in the audio spectrum range.
The other components required for a videoconferencing system include:

Video input: video camera or webcam
Video output: computer monitor, television or projector
Audio input: microphones, CD/DVD player, cassette player, or any other source of
PreAmp audio outlet.
Audio output: usually loudspeakers associated with the display device or telephone
Data transfer: analog or digital telephone network, LAN or Internet
There are basically two kinds of videoconferencing systems:

1. Dedicated systems have all required components packaged into a single piece of
equipment, usually a console with a high quality remote controlled video camera.

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